The crystal structure of Delta(3)-Delta(2)-enoyl-CoA isomerase

The active-site geometry of the first crystal structure of a Delta (3)-Delt a (2)-enoyl-coenzyme A (CoA) isomerase (the peroxisomal enzyme from the yea st Saccharomyces cerevisiae) shows that only one catalytic base, Glu158, is involved in shuttling the proton from the C2 carbon atom of the substrate, Delta (3)-enoyl-CoA, to the C4 atom of the product, Delta (2)-enoyl-CoA. S ite-directed mutagenesis has been performed to confirm that this glutamate residue is essential for catalysis. This Delta (3)-Delta (2)-enoyl-CoA isom erase is a hexameric enzyme, consisting of six identical subunits. It belon gs to the hydratase/isomerase superfamily of enzymes which catalyze a wide range of CoA-dependent reactions. The members of the hydratase/isomerase su perfamily have only a low level of sequence identity. Comparison of the cry stal structure of the Delta (3)-Delta (2)-enoyl-CoA isomerase with the othe r structures of this superfamily shows only one region of large structural variability, which is in the second turn of the spiral fold and which is in volved in defining the shape of the binding pocket. (C) 2001 Academic Press .